How does tolerance develop?
- By Robert Mauer
- Reviewed by: Dr. Janaka Hanvey, PhD
Tolerance develops when the brain adapts to repeated drug exposure, reducing the drug’s effect over time. As a result, a person may need larger amounts of the substance to achieve the same effect they initially experienced.
This adaptation occurs through changes in receptor sensitivity, neurotransmitter release, and overall brain responsiveness. In some cases, tolerance develops quickly; in others, it builds gradually over longer periods of use.
Tolerance increases risk because higher doses can lead to greater harm, including overdose. It is also one of the pharmacologic criteria used in diagnosing substance use disorders, although it must be interpreted in the context of the overall pattern of use.
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Sources
National Institute on Drug Abuse (NIDA) — Drugs, Brains, and Behavior: The Science of Addiction
Government scientific overview of drug use, addiction, brain changes, tolerance, dependence, and recovery.
National Institute on Drug Abuse (NIDA) — Commonly Used Drugs Charts
Comprehensive federal reference covering major drug categories, effects, overdose risks, and health consequences.
Substance Abuse and Mental Health Services Administration (SAMHSA) — Substance Use and Mental Health
Federal information about substance use, addiction, prevention, treatment, and behavioral health.
MedlinePlus — Drugs and Young People
Government medical resource discussing drug effects, misuse, addiction risks, and substance use education.
National Institute on Drug Abuse (NIDA) — Understanding Drug Use and Addiction DrugFacts
Clear explanation of why people use drugs, how addiction develops, and how substance use affects the brain and behavior.